I wrote my dissertation on the underdetermination of theory by data. I managed to turn material from my thesis into almost ten free standing papers, but despite some perfunctory efforts I never turned my work on underdetermination into a book. I thought I might finally write that book when I went to Pittsburgh in Fall 2010.

About the same time, I started working on natural kinds. I expected to write a couple of papers on the topic. Yet the project grew larger, and I ended up writing a book on natural kinds during my semester of sabbatical.

Both 'underdetermination' and 'natural kinds' are items of philosophical jargon which are usually presupposed to be well-defined and univocal. Yet both are also used in a tremendous variety of ways, and the literature includes authors' unwittingly using the terms in different ways.

'Underdetermination' is often taken to be a label for the so-called Duhem-Quine Problem but also for the Problem of Empirically Equivalent Rival Theories. It is also sometimes taken to include riddles of induction (Hume's, Goodman's, or both) or quotidian cases of curve-fitting. These are very different things. So one possible diagnosis is just that the word is used in a confused way.

In my thesis, I found a way to characterize underdetermination so that all of these different issues turned out to be varieties of the same thing. The basic idea is that a case of underdetermination involves a set of rival theories, a standard for what will count as responsible choice between them, and a scope of circumstances in which responsible choice is impossible. The disparate things travelling under the banner 'underdetermination' can be obtained by filling in these three parameters in different ways.

This was kind of a neat trick, but the problem was there was really no useful work done by having the big umbrella term. The analysis shows merely that there is a way to make sense of 'underdetermination' talk, not that you really ought to have it as a term in your vocabulary. Many specific varieties of underdetermination have important consequences, so I wrote papers about those. I could not see how to write one sensible book covering all the disparate stuff.

'Natural kind' is similarly used as a label for many different things: categories which support induction, categories with essences, categories that ought to appear in a scientific account of the world, categories which we rigidly designate, and so on. Again, these are very different things. So you might just throw up your hands.

Yet the conception of 'natural kind' which I defend in the book does not vindicate all these different presumptions. I do not treat natural kinds as needing to have essences, and I am neutral on the question of how natural kind terms refer. So what I offer is more an explication than an analysis.

I think that 'natural kind' in the sense which I defend in the book does important philosophical work. It is useful for framing questions about whether Pluto is really a planet, about the reality of species, and so on.

I had not even explicitly noticed that my work on underdetermination had headed into a cul-de-sac. It was only after I had completed the manuscript for my book that I realized that I really do not think that 'underdetermination' is an especially helpful term to have in our philosophical vocabulary but that 'natural kind' is.

To put the point concisely: 'Underdetermination' is not a natural kind for philosophy of science, but 'natural kind' is.

Even more concisely: Yay explication and 'natural kind'! Boo analysis and 'underdetermination'!

My colleague Jon Mandle has been looking at John Rawls 1950 doctoral dissertation, A Study in The Grounds of Ethical Knowledge. Jon asked me about a section in which Rawls contrasts ethical theory and scientific theory. The philosophy of science that he presumes is really just background. Yet he discusses what is now often called the Duhem-Quine Problem, a couple of years before Quine's "Two Dogmas of Empiricism". So where did Rawls get it from?

I did not have a good answer to this, beyond the obvious suggestion. So I decided to share the interesting bit here.

When I learned about the recent collection Carving nature at its joints: Natural kinds in metaphysics and science, I had to change the title of my forthcoming book. After much discussion here, on other blogs, and on Google+, and after some back and forth with the publisher, my book will be Scientific enquiry and natural kinds: From planets to mallards. (A better title, I think. So the rigamarole was worth it.)

I learned about the Carving collection when I was asked to review it for Notre Dame Philosophy Reviews. I love open-access journals in general and NDPR in particular, so I was glad to do it. My hatchet job review has now been published over on the NDPR site.